Hot metal level detector



Aug. 6, 1968 R. E. WOODCOCK 3,395,908

HOT METAL LEVEL DETECTOR Filed Oct. 24, 1965 INVENTOR. Hay F. fi oodcocfi.

arroezvn United States Patent Filed Oct. 24, 1965, Ser. No. 504,772 6 Claims. Cl. 266-34) ABSTRACT OF THE DISCLOSURE I Apparatus for positioning an oxygen lance within a basic oxygen converter, and more specifically apparatus for detecting the level of the hot metal bath in a basic oxygen converter by means of a pair of conductive probes extending downwardly below the lower end of the lance.

In the basic oxygen furnace process, molten metal is introduced into a vessel and a premeasured amount of scrap metal is added. The scrap metal will generally gravitate to the bottom of the vessel, the scrap metal quantity generally being of a magnitude less than that of the molten metal. Floating on top of the molten metal is a slag layer which is usually introduced along with the molten metal. The thickness of the slag layer varies from melt to melt, thereby making it ditficult to ascertain the specific level of the molten metal. After the proper ingredients are contained within the vessel, a tube, known as an oxygen lance, is introduced into close proximity with the molten metal, whereupon oxygen is released into the vessel to oxidize impurities in the metal and to create a chemical reaction with the metal, resulting in an increased amount of heat which aids in melting the scrap metal. Inasmuch as the velocity of the oxygen emanating from the oxygen lance is critical and controlled within limits, it is necessary to know the exact height of the lance tip above the slagmetal line. The oxygen must not only be able to separate the slag, but it must be able to penetrate the molten metal to a sufiicient depth to create the chemical reaction and, additionally, to impart a circulatory movement to the molten metal itself. Consequently, it is important that the position of the lance tip be known at the start of the blow with a fair degree of accuracy.

Accordingly, it is an object of this invention to provide a method for positioning an oxygen lance within a basic oxygen converter.

It is another object of this invention to provide a method for positioning an oxygen lance a given distance above the slag metal line regardless of the thickness of the slag layer.

The foregoing objects of this invention are accomplished by providing a pair of conductive rods afiixed to and insulated from the oxygen lance. A first conductive rod extends below the lance tip a known distance. The second conductive rod extends below the first rod some arbitrary distance. The upper ends of the conductive rods are electrically connected to a level indicator which may consist of an ohmmeter, or as an alternative, a voltage source and an ammeter. As the lance is lowered toward the hot metal, the rods contact first the slag layer, and due to the conductivity of the slag, some indication is given on the level indicator. However, due to the greater conductivity of the hot metal when the first conductive rod makes contact with the slag-metal line, an indication is given by the indicator which establishes a reference position for the lance tip above the hot metal line. Changes in the height of the lance with respect to the hot metal can then be made as desired.

Further objects, features, and advantages of the invention will become apparent from the following description when taken in conjunction with the accompanying draw- 3,395,908 Patented Aug. 6, 1968 ing in which FIGURE 1 and 2 show a partially schematic, partially diagrammatic representation of the invention.

Referring now to the drawing, there is shown in FIG- URE 2 a vessel generally designated as 10 which is composed of an outer steel shell 12 and an inner fire brick lining 14. Within the vessel 10 is a bath of molten metal 16 which contains the scrap metal charge (not shown) and floating on top of the metal 16 is a layer of slag- 18 which thickness can vary. An oxygen lance 20 is depicted in FIGURE 1 in its raised position prior to the start of the blow. Affixed thereto is a pair of conductive rods 22 and 24, the rods being made of steel and suitably insulated with an asbestos covering which serves as a thermal insulation as well as an electrical insulation. As shown in the drawing, the conductive rods 22 and 24 are spaced apart, although the spacing around the circumference of the lance 20 is not critical but is shown merely for illustrative purposes. The first conductive rod 22 is positioned so that it extends below the tip of the oxygen lance 20 a specified known distance designated as X" on the drawing. The second conductive rod 24 extends below the first rod 22 an additional distance so that the second rod 24 comes into contact with the molten metal first, thus insuring positive indication when the first rod 22 ultimately comes into contact with the metal bath 16. The conductive rods 22 and 24 are secured to the lance 20 by any suitable means, such as bands 26. The upper ends of the conductive rods 22 and 24 are electrically connected to a remote level indicator 30 by a pair of electrical conductors 28. The remote level indicator 30 is a conductivity sensitive device such as an ohmmeter, or as an alternative, it may consist of a voltage source in series with an ammeter and both connected in series with the conductive rods 22 and 24. Thus, there is a series circuit from one rod 24 through its respective conductor 28, to one terminal of the level indicator 30 to the other terminal of level indicator 30, through the other conductor 28 and the conductive rod 22, the circuit being completed by the molten metal 16.

In operation, the lance 20 is lowered into the vessel 10, and when the second conductive rod 24 comes into contact with the slag layer, a reading is given on the indicator 30. However, due to the greater conductivity of the metal 16 as compared with the slag 18 upon further travel of lance 20, the indicator 30 will show an abrupt change in reading when both conductive rods 22 and 24 have reached the top of the hot metal bath 16 (this position being indicated on the drawing by dotted lines). This establishes a reference for lance positioning at the actual height of the hot metal bath 16. At this time the lance 20 can then be raised to the desired height above the bath, and the flow of oxygen is started through the lance 20 to begin the blow. Inasmuch as the conductive rods 22 and 24 are usually melted off during the blow, the apparatus is constructed so that the conductive rods 22 and 24 can readily be changed between blows.

While there has been shown and described a specific embodiment as required by the patent statutes, other adaptations and modifications may be made without departing from the spirit and scope of the invention.

I claim:

1. In combination, a basic oxygen converter adapted to contain molten material, an oxygen lance reciprocable toward and away from the level of said molten material in the converter, a pair of spaced conductive members arranged for reciprocable movement with the oxygen lance, each of said members extending at least a given distance below the lower tip of said lance, an indicator having a pair of terminals, and means for electrically connecting each of said terminals to the respective conductive members, said conductive members being electrically insulated from each other-when not immersed in Said molten material-topresent an open circuit to-said indicator, the conby the height of said lance above the level of saicl molten material is at'said given distance and can be determined by theindication of.-said indicator for maximum conductivity. I

2. A device according to claim 1 wherein said conductive members are steel rods insulated with asbestos.

3. A device according to claim 1 wherein said conductivemembers are afiixed to and insulated from said oxygen lance.

4. A device according to claim 1 in which one of said conductive members extends below the tip of the oxygen lance a distance greater than said given distance.

i I A device according to claim 1 wherein said indicator comprises an-ohmmeter; 6. A device according to claim 1 wherein said indicator comprises a voltage source and an ammeter in series.

References Cited V I I I UNITED STATES PATENTS 2,763,935

J. SPENCER OVERHOLSER, Primary Examiner. E. MAR, Assistant Examiner. I 

